2+cos2 x -3 cos x =0

Question

2+cos2 x -3 cos x =0

Answer 1

2+2сos²x-1-3cosx=0
cosx=a
2a²-3a+1=0
D=9-8=1
a1=(3-1)/4=1/2⇒cosx=1/2⇒x=π/3+2πk U x=-π/3+2πk,k∈z
a2=(3+1)/4=1⇒cosx=1⇒x=2πk,k∈z